Straddle carrier

ABSTRACT

The straddle carrier has two spaced parallel elongated frame members adapted to straddle a load. A vertically disposed arch member connects the frame members together adjacent one end thereof and diagonally disposed leg members connect the tops of the arch to substantially the mid-points of the frame members. Ground wheels are flexibly mounted on the undersides of the frame members, and means for steering the wheels are provided. A rectangular load lifting beam is disposed between the frame members and arches. Means are provided engaging the four corners of the lifting beam for raising and lowering the lifting beam, means being provided at the four corners of the lifting beam for securing same to a load. Means are also provided for guiding the lifting beam during its ascent and descent. And means are provided for controlling the lifting beam raising and lowering means whereby the four corners of the beam will be simultaneously raised or lowered equal amounts notwithstanding the relative weights on the respective corners, in order to maintain the beam always parallel with the frame members.

United States Patent Monk [54] STRADDLE CARRIER [72] Inventor: John Thomas Monk, 405 Meadow Moss Drive, Jackson, Miss. 39206 [221 Filed: Sept. 15, 1970 [21] Appl. No.: 12,444

[52] US. Cl ..2l4/394 [51] Int. Cl. ..B60p 1/02 [58] Field of Search ..2l4/390, 392, 394, 396

[56] References Cited UNITED STATES PATENTS 2,603,369 7/1952 Soderstrom ..2l4/396 3,008,424 11/1961 Roth ..180/66 F 3,344,940 10/1967 Burgess et al ..214/394 3,452,892 7/1969 Modenesi ..214/394 3,494,491 2/ 1970 Toyotaro Sumida ..2l4/394 FOREIGN PATENTS OR APPLICATIONS 693,137 8/1964 Canada ..214/392 Primary Examiner-Robert J. Spar Attorney-Alexander & Dowell [451 Nov. 21, 1972 [S 7] ABSTRACT The straddle carrier has two spaced parallel elongated frame members adapted to straddle a load. A- verti-' cally disposed arch member connects the frame members together adjacent one end thereof and diagonally disposed leg members connect the tops of the arch to substantially the mid-points of the frame members. Ground wheels areflexibly mounted on the undersides of the frame members, and means for steering the wheels are provided. A rectangular load lifting beam is disposed between the frame members and arches. Means are provided engaging the four comers of the lifting beam for raising and lowering the lifting beam, means being provided at the four corners of the lifting beam for securing same to a load. Means are also provided for guiding the lifting beam during its ascent and descent. And means are provided for controlling the lifting beam raising and lowering means whereby the four comers of the beam will be simultaneously raised or lowered equal amounts notwithstanding the relative weights on the respective corners, in order to maintain the beam always parallel with the frame members.

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PATENTED NW 2 1 I972 SHEET 08 or 1 a TOR. I W1 INVEN PATENTEDnum m2 sum 11 or 14 INVENI'OA %"4 M PATENTED NOV 2 1 m2 SHEET lEUF 14 INVENTo/Z P'A'TE'N'TEDunvzu m2 sum 13 0F 14 STRADDLE CARRIER DESCRIPTION OF INVENTION This invention relates to straddle carrier type material-handling vehicles so designed that the load to be carried is suspended within the framework of the vehicle, the vehicle may be of such size and proportions as to permit engaging, hoisting, stacking and transporting van-sized containers.

Prior art machines of this type are subject to very high accident rates caused by poor visibility. They have mechanical failures caused by weak frame structures and complicated lift systems.

The principal objects of my invention are to provide a straddle carrier which has excellent visibility and a strong, simple, smooth structure. These objectives are attained in numerous ways, some of which are as fol-' lows:

The main frame of my invention consists of spaced parallel elongated frame members which are connected together adjacent one end by means of a vertically disposed structural arch to form a rigid rectangular frame. Said arch carries adjacent its upper end the cab for the driver in which is disposed the steering wheel and various controls for the vehicle. The arch is braced by a diagonal leg connecting the arch adjacent its upper ends to substantially the mid-points of the frame members.

Supporting wheels are flexibly applied to the underside of the frame members, three wheels being provided on each side below each frame member, the center wheels of which are fixed, while the outer wheels are simultaneously actuated regardless of the radius of curvature of any steering course in such manner that the projection of the axles of the outer wheels, both those of the inner frame and outer frame members, will always intersect the projection of the axles of the center wheels at a common point for all radii of curvatures in steering.

Within the vehicle is a container lifting beam comprising an outer member and an inner member, the former being shiftable laterally and longitudinally with respect to the inner member. The ends of the inner member of the lifting beam extend beyond the ends of the outer member and carry at the comers thereof rollers adapted to engage telescoping guides disposed on or adjacent the legs of the arch to guide the lifting beam during its vertical ascent and descent. Adjacent the guides are upwardly disposed fluid cylinders carrying upwardly extensible rams, said cylinders being connected with their respective frame members by self aligning bearings to permit universal movements of the upper ends of the cylinders. The corners of the outer member of the lifting beam are connected to one end of cables extending from said corners up and over pulleys on the upper ends of the respective rams, the other end of the cables being connected to the frame members adjacent the upper end of the cylinders, whereby as the rams of the hydraulic cylinders are extended upwardly by hydraulic pressure the four corners of the lifting beam will be simultaneously raised or lowered to thereby raise or lower a van-sized container or the like which is attached at its four corners to the underside of the lifting beam at the four corners thereof by conventional coupling members. Means are provided for simultaneously actuating the cylinders to raise or lower the lifting beam and the van-sized container attached thereto within the frame of the vehicle, said means including a fluid circuit so arranged that the said corners of the lifting beam are simultaneously raised or lowered equal amounts notwithstanding the relative weights on said respective corners, so as to maintain the van-sized container at all times parallel with the machine frame.

Heretofore, straddle carriers have been provided in which the frame is of general horizontal U-shape, i.e., in a horizontal plane, the frame being open at one end only, the same having a connecting arch at one end only, but it has been found that the stresses imposed are I on such long moments that it is very difficult to prevent frame breakage in the center section of the arch; and in order to help this situation the lift cylinders on such prior art machines have been rigidly mounted on the frame and were connected at their upper ends with a cross member; but it has been found that this imposes severe bending loads on the lift cylinders, and results in broken cylinders and severe wear on the piston and sealing leathers,

Another object of my invention is to provide rigid rectangular frame having a connecting arch near one end, of such strength as to require no other connection, the outer rounded ends of the frame members acting as guides for the container as it passes between the frame members. In my design the lift cylinders being connected with the frame members by universal joints, leaves the lift cylinders free of all outside bending stresses and they support only the load.

Heretofore, such prior art machines have been provided in which the lift cylinders have been connected together with a cross member from which the lifting beam is suspended; but in my design the lifting beam is suspended directly from the lift cylinders. This removes another obstruction to vision.

Heretofore, in such prior art machines the vertical guide tracks for the lifting beam having been attached directly to the cross members which connect the lift cylinders and the guide tracks move up or down with the cross member. Further, the tracks are restrained by guide bars in the side frame members and are subjected to loads imposed by the frames.

Another object of my invention, however, is to provide a construction in which the vertical guide tracks are stationary until such time as the lifting beam rises to the tops of the arch, after which the guide tracks are raised by the guide rollers on the ends of the lifting beam engaging plates at the tops of the tracks. When the beam is lowered, the tracks descent until they reach the starting point, at which place they stop, but the lifting beam is free to continue its downward movement without further movement of the guide tracks. No stresses can be transferred from the frame to the guide tracks.

l-leretofore in such prior art machines, the lifting beam itself is usually suspended some distance from the point where it attaches to the load. Hence a cantilever or bending load is imposed on the lifting beam. However, a further object of my invention is to provide an arrangement in which the lifting cables for the lifting beam attach directly over the point where the load itself is lifted; therefore my lifting beam supports nothing, but merely acts as a spacer to keep the lifting hooks or twist locks in proper relation to one another.

design which removes all power components from high elevations and places them low in the structure where they contribute to stability, and are low enough to'be reached from a ladder, or may be removed by use of a small fork-lift, common everywhere. In my design there are no members connecting-the lift cylinders to interfere with theoperators vision, and no power train components surround the operator. Furthermore, there are no horizontallyextending frame members in the upper side frames to further restrict vision.

In such prior art machines a long chain drive is used for each drive wheel, reaching from the power platform to the drive wheel, which chain limits the amount the drive wheels can cut, or steer, and for that reason they must resort to uneven spacing of the support wheels, involving severe steering angles on those furthest from the drive wheels. It has been found that in order to secure an acceptable turning radius, the, machine must have a short wheelbase. This results in instability in a fore-and-aft direction. The projecting chain and guard are frequently damaged in collision accidents.

, A still further object of my invention therefore is to provide a design which uses hydraulic or hydrostatic power which is transmitted to the drive wheels through flexible hose. For that reason the steering angles can be whatever the designer fancies up to and including a 90 cut." This makes it possible to space the wheels evenly on the machine, which in turn makes it unnecessary to steer the center wheels and hence provides simpler steering. Since the steering angles can be greater,- it is no longer necessary to keep the wheelbase short and therefore it may be made longer with improvement in ifore-and-aft stability. As in my design there are no chains and guards to knock off, another set of problems are eliminated. Other minor object will be hereinafter set forth.

I will explain the invention with reference to the accompanying drawings, which illustrate several practical embodiments thereof, to enable others familiar with the art to adopt and use the same; and will summarize in the claims the novel features of construction, and novel combination of parts, for which protection is desired.

In said drawings:

FIG. 1 is a side elevation of my novel straddle carrier showing the lifting beam in the lowered position.

FIG. 2 is a side view similar to FIG. 1, but showing the lifting beam in elevated position.

FIG. 3 is an end elevation of the carrier shown in FIG. 1 showing at said end the arch and cab mounted thereon.

' FIG. 3A is an end elevation of the carrier shown in FIG. 1, showing the end opposite from that shown in FIG. 3, and showing the relation between the beam frame and lift cylinders, and showing that the cylinders lean inwardly.

FIG. 4 is an end elevation of the carrier shown in FIG. 2, but showing the lifting beam elevated.

FIG. 4A is an end elevation of the carrier opposite from that shown in FIG. 4, but showing the lifting beam elevated, and also showing that the cylinders lean inwardly.

FIG. 5 is a top plan view of the carrier.

FIG. 5A is a top plan-view of the carrier but an alternate beam shift, omitting the fore-and aft cylinder. I v i l 1 FIG. 6 shows a schematicplan of the beam shift hydraulic system.

FIG. 7 shows a schematic plan of the beam lift and levelingsystem, and also showing the electrical circuit forsame, FIG. 8 shows a plan of the sensor device in neutral. FIG. 8A shows an end elevation of the device shown inFIG. 8.

FIG. ,9 shows a plan elevation of the sensor of FIG. 8 in the increased tension position. I

FIG. 10 shoes a plan elevation of the sensor of FIG. 8 in the decreased tension position.

FIG. 11 shows in schematic elevation how the sensor cable 50 is attached to the beam and cylinders in order to sense differences in cylinder extensions.

FIG. 12 shows the same as FIG. 11 but for cable 50a.

FIG. l3'shows the same as FIG. 12 but for cable 50b. FIG. 14 shows a detail. FIG. 15 shows a detail."

The rectangular main frame of the vehicle as shown in FIGS. 1, 2, 3, '3A, 4, 4A ands is comprised of two spaced parallel elongated frameme'mbers and 71 formed of structural plates and angle bars, or of square tubing, connected to one another adjacent to one end only thereof by an arch 72 formed of structural plates and angle bars,saicl arch-72 being of substantial construction and-serving to keep the main frame members 70 and 71 in proper spaced relation with one another,

and to provide clearance for the frame to straddle -'a load to be handled from either end thereof. Said arch 72 is comprised of vertical legs 72a and-72b, diagonal legs 73 and 730, the lower ends of which rest upon and wheels 75, 75a and 75b, under frame member 70; and

wheels 76, 76a, 76b, under frame member 71. The wheels are attached tothe frame 70, 71 with trunnions which allow vertical movement as well as rotative movement about the vertical axis of the trunnions. The center wheels (when used) 75a and 760 are attached to frame members 70 and 71 respectively with linkages 77, 77a which prevent their rotation about the vertical axes of the trunnions, and thus cause wheels 75a and 76a to remain always parallel with the axis of the main frames 70and 71 respectively. The wheels 75 and 75b are connected with a linkage system in such a way as-to cause them to steer equal but opposite angles. The wheels 76 and 76b are connected with a linkage system showing in such a way as to cause them to steer equal but opposite angles. Wheels 75 and 75b are connected to wheels 76 and 76b with a linkage system in such a way as to cause them to turn about a common point whenever the machine is traveling in any way but a straight line direction. The force to operate the steering mechanism is supplied by an engine driven hydraulic pump 78. The steering is controlled by an operatorcontrolled valve connected to a steering wheel mounted in cab 79.

The operator is housed in the cab 79 mounted on the front face of cross beam 720 of the arch 72, in such a manner as to give the best visibility possible. All controls for driving or hoisting are also located in cab 79.

The engine 80 for hoisting and propulsion is mounted on frame member 70 near the arch 72 as shown in FIGS. 1 and 2. The engine 80 has several hydraulic pumps mounted upon it which furnish the power to operate various functions of the vehicle. The engine 80 provides the power for propulsion of the vehicle by means of avariable displacement hydraulic pump 81 mounted thereon and connected to hydraulic motors 82 and 82a in two (or more) of the wheel hubs by means of suitable pipe and hose connections.

The frame of the vehicle also supports the lift mechanism and guidance system for the load to be lifted. The various systems and devices used to lift and control the load lifted will be described in detail in subsequent paragraphs. In general it comprises four free hydraulic cylinders 7, 7a, 7b, 70, FIGS. 1, 2, 5 and 5A, supported on the main frame members 70 and 71 by use of self aligning bearings 12. The cylinders 7 and 7a and their rams 8, 84, project through openings in the diagonal legs 73 and 73a near their upper ends as shown in FIGS. 5 and 5A, and are loosely confined therein. The cylinders 7b and 7c and their rams 8b and 8c respectively are mounted in columns 74 and 74a, FIGS. 3A, 4A and 5A. The columns 74 and 74a serve to protect the cylinders 7b, 7c and rams 8b, 8c from collision damage, and also to provide anchor points 13b and 13c for cables 11b and 11c. Supports 74b and 74c prevent cylinders 7b and 7c from falling inwardly under no-load conditions.

The lift mechanism described herein is intended to lift or lower an object or adapter beam by use of double acting hydraulic cylinders and rams. Each ram has a sheave attached directly to its exposed upper end and is not directly connected without another ram. The cylinders and rams do not stand vertical or parallel, but lean inwardly at their upper ends as shown in FIGS. 3A and 4A. All of the lift cylinders are identical in components and operation.

Hydraulic fluid is carried in tank 1, FIGS. 1 and 7, pumped by engine driven pump 2 to operator controlled valve 3. When valve 3 is in neutral or hold" position, fluid circulates through valve 3 and back to tank 1. The other connections are closed. The valve 3 is an open-center type designed to be used with double acting cylinders. When pressure from pump 2 is applied to one outlet port the other communicates with the its respective cylinder 7, 7a, 7b, thereby extending the related ram 8, 8a, 8b, 8c, which carries sheave 9, 9a, 9b, 9c, upwardly, and raises the lifting beam 10 through the action of tensile member 11, 11a, 11 b, 110, FIGS. 2, 3, 4 and 4a. Tensile members 11, 11a, 11b, 110 are attached to the beam 10 each to one end thereof and to the frame structure of the machine at the other end 13, 13a, 13b, 13c (FIG. 5A) adjacent the upper end of the corresponding cylinder 7, 7a, 7b and 70. A pressure relief valve 101, 101a, 101b, 1010 (FIG. 7) limits the maximum pressure which can be supplied to check valves 6, 6a, 6b, 60, respectively by the flow divider 5. Excess pressure is dissipated through line 19 to tank 1.

The cylinders 7, 7a, 7b, 7c are attached to the frames 70, 71 of the machine only at their bases, and each is supported on a self-aligning bearing 12 (FIGS. 1 and 2) in such a manner as to allow the movement of its upper end in all planes. The cylinders 7, 7a, 7b, 7c, and rams 8, 8a, 8b, 8c, are thus free to equalize the forces acting on lifting beam 10 and anchors 13, 13a, 13b, 13c through the tensile members 11, 11a, 11b, 110, without being subjected to any bending loads.

When the operator moves the control 4 (FIG. 7) to the Down position, fluid flows through valve 3 through line 14 to cylinders 7, 7a, 7b, 70, at points 15, 15a, 15b, 150, respectively, and to the pilot pistons in valves 6, 6a, 6b, 60 causing same to open. Fluid may then escape from beneath the rams 8, 8a, 8b and 8c and through valves 6, 6a, 6b, 6c, and back to the tank 1 by way of flow divider 5 and valve 3. Unless pressure is exerted on the pilot pistons in valves 6, 6a, 6b, 6c the valves will close and stop downward movement of the rams 8, 8a, 8b, 8c. If the downward movement of ram 8, 8a, 8b, requires more fluid than is supplied by the engine driven pump 2, the pressure will fall in line 14 and the pilot pistons in valves 6, 6a, 6b, 6c will close. Pressure applied at the upper side of the ram pistons at points 15, 15a, 15b, 15c, forces the rams downwardly. If the load on sheaves 9, 9a, 9b, 9c cause it to descend faster than fluid' is supplied to points 15, 15a, 15b, 15c, the pressure in line 14 will become too low to hold the pilot check valves open in valves 6, 6a, 6b, 6c, and the ram will stop. Thus it is possible for the operator to control the speed of both ascent and descent of the lifting beam 10 by controlling the speed of the engine and hence the volume of fluid delivered by pump 2.

In order to insure that all rams will be displaced approximately equal amounts despite variations of load and internal leakage, it is necessary to further refine or trim the system. Therefore, means of sensing uneven extensions of the rams 8, 8a, 8b, and 8c, is devised. A system (FIGS. 11, 12, 13) of cables pulleys, sensors (FIG. 8), and solenoid valves (FIGS. 7, ll, 12 and 13, is used to accomplish this end.

The sensor (FIGS. 8, 9, 10) is intended to sense changes in the tension of the cable 50 threaded through it and to translate said information into an electrical signal. Base 20 (FIG. 8) has an axle 21 upon which lever 22 is mounted. Said lever is supported by bearings between axle 21 and base 20 so that the lever 22 may move in a plane parallel to the base 20. Mounted on lever 22 are pulleys or sheaves 23 and 24 which are free to rotate on their respective axles. Two Micro switches 27 and 28 are mounted on the base 20 ina position which will allow the free end of the lever 22 to operate the linkage in switches 27 and 28 and cause the contacts to close or open as the lever is moved along its arc. Means are provided to alter the position of these switches 27 and 28 in relation to lever 22 so that the sensitivity of the device may be controlled. Two lugs 29 and 30 are attached to base 20 in such a way as to prevent lever 22 from traveling far enough to overrun the actuating linkage for switches 27 and 28. In FIG. 8 the device is shown in neutral or no-signal position. In this view the cable 50 tension has been adjusted so that spring 26 has been overcome enough to allow lever 22 to rest in the mid-point of its travel. The switches 27 and 28 are positioned so that their linkage is approximately equidistant from the free end of lever 22. This condition will be referred to as the neutral position. The switches themselves could either be closed or open depending on the requirements of the application. In this illustration all switches will be of the normally open type. If normally closed type are used the flow of current would be interrupted in FIGS. 9 and 10. FIG. 9 shows what happens when the tension on cable 50 is increased enough to further overcome spring 26 and thus cause the lever 22 to depress the linkage of switch 28 thereby closing the related circuit. FIG. 10 shows what happens when the tension on cable 50 is decreased enough to allow the spring 26 to retract lever 22 causing it to depress the linkage in switch 27 and thereby close related circuit.

FIGS. 7 and 11 show that at the base of each cylinder 7, 7c and communicating with the hydraulic fluid within same, there is mounted a respective solenoid controlled valve 16, 16c, of the normally closed type. Fluid passing through the valves 16, 16c is returned to the tank 1 by line 19. This solenoid valve has one end of its coil attached to an electric power source 1 such as a storage battery, the other end of the coil being attached to the corresponding switch in sensor 18. It can be seen in FIG. 7 that switch 28 is connected to solenoid 160, also that switch 27 is connected to solenoid In FIGS. 11, 14 and 15, cable 50 is attached to ram 8c at point 51, and is threaded under sheave 52 and thence through sensor 18 and under sheave 53, and over sheave 54 which is attached to ram 8, and under sheave 55 which is attached to lifting beam 10 with its outer end attached to ram 8 at point 54a. As the lifting beam 10 is elevated cable 50 is paid out between sheaves 55 and 54 twice as fast as the increase in distance between sheaves 54 and 53. Therefore the tension on cable 50 will remain constant as long as rams 8 and 80 extend or retract an equal amount, and the sensor 18 will remain in neutral, as in FIG. 8.

If ram 8c extends more than ram 8, the tension on cable 50 will be increased and this will be detected by sensor 18 (FIG. 9). The increase in tension will cause the switch 28 to close and thus energize the solenoid valve 16:: (FIG. 7), opening the said valve and allowing fluid to escape from cylinder 70. This will allow ram 8c to descend until the cable tension decreases enough to allow sensor 18 to return to neutral position, as in FIG. 8, thus breaking the circuit and allowing valve 160 to close again.

If ram 8 extends more than ram 80 the tension on cable 50 will decrease and this will be detected by sensor 18 (FIG. 9). This decrease will cause switch 27 to close and thus energize the solenoid valve 16 (FIG. 7 opening the said valve and allowing fluid to escape from cylinder 7. This will allow ram 8 to descend until the cable tension increases enough to allow sensor 18 to return to neutral as in FIG. 8, thus breaking the circuit and allowing valve 16 to close again.

The system shown in FIGS. 7, 11, 14 and 15 will cause rams 8 and 8c to maintain the same amount of extension as long as electrical energy is supplied. Since it provides an independent. means for the escape of fluid from beneath the rams 8 and 8c it will operate whether the rams are ascending, descending, or stationary. I

In FIGS. 7 and 12 at the base of each cylinder 7, 7a and communicating with the hydraulic fluid within same, is mounted a respective solenoid controlled valve 16, 16a of the normally closed type. Fluid passing through the valve 16, 16a is returned to the tank 1 by way of line 19. This solenoid valve has one end of its coil attached to an electric power source 17 such as a storage battery, the other end of its coil being attached to the corresponding switch in sensor 18a. It can be seen in FIG. 7 that the switch 28a is connected to solenoid 16. Also that switch 27a is connected to solenoid 16a.

In FIG. 12, cable 50a is attached to ram 8 at point 56 and is threaded through sheaves 57, 58, sensor 18a, through sheaves 59, 60, through sheave 61 which is attached to ram 8a, through sheave 62 which is attached to lifting beam 10 and is attached to ram 8a at point 61a. As the lifting beam 10 is elevated, cable 50a is paid out between sheaves 61 and 62 twice as fast as the increase in distance between sheaves 60 and 61, therefore the tension on cable 50a will remain constant as long as rams 8 and 8a extend or retract an equal amount, and the sensor 180 will remain in neutral as in FIG. 8.

If ram 8 extends more than ram 8a, the tension on cable 50a will be increased and will be detected by sensor 18a (FIG. 9). The increase in tension will cause the switch 28a (FIG. 7) to close, and thus energize the solenoid valve 16, opening the said valve and allowing fluid to escape from cylinder 7. This will allow the ram 8 to descend until the tension on cable 50a decreases enough to allow sensor 18a to return to neutral position (FIG. 8). This will break the circuit allowing valve 16 to close.

If ram 8a extends more than ram 8 the tension on cable 50a will decrease and this will be detected by sensor 18a (FIG. 10). This decrease will cause switch 27a to close and thus energize solenoid valve 160 (FIG. 7), opening the valve and allowing fluid to escape from cylinder 7a. This will cause ram to descend until the cable 500 tension increases enough to allow sensor 18a to return to neutral (FIG. 8). This will break the circuit allowing valve 16 to close.

The system shown in FIG. 12 will cause rams 8 and 8a to maintain the same amount of extension as long as electrical energy is supplied. Since it provides an independent means for the escape of fluid from beneath rams 8 and 8a it will operate whether the rams are ascending, descending or stationary.

In FIGS. 7 and 13 at the base of each cylinder 7a, 7b and communicating with the hydraulic fluid within same, is mounted a solenoid controlled valve 16a, 16b. This valve is of the normally closed type. Fluid passing through valve 16a, 16b, is returned to the tank 1 by way of line 19. This solenoid valve has one end of its coil attached to an electric power source 17 such as a storage battery, the other end of the coil is attached to the corresponding switch in sensor 18b. It can be seen in FIG. 7 that switch 28b is connected to solenoid valve 16a, also that switch 27b is connected to solenoid valve 16b.

In FIG. 13, cable 50b is attached to ram 8a at point 63 and is threaded through sheave 64, sensor 18b, through sheave 65, through sheave 66 which is attached to ram 8b, through sheave 67 which is attached to lifting beam 10, and cable 50b is attached to ram 8b at point 66a. As the lifting beam is elevated cable 50b is paid out between sheaves 66 and 67 twice as fast as the increase in distance between sheaves 65 and 66; therefore the tension on cable 50b will remain constant as long as rams 8a and 8b extend or retract an equal amount, and the sensor 18b will remain in neutral as in FIG. 8.

If ram 8a extends more than ram 8b the tension on cable 50b will be increased and will be detected by sensor 18b (FIG. 9). The increase in tension will cause the switch 28b to close and thus energize the solenoid valve 16a (FIG. 7) opening the said valve and allowing fluid to escape from cylinder 7a. This will allow the ram 8a to descend until the tension on cable 50b decreases enough to allow the sensor 18b to return to neutral position (FIG. 8). This will break the circuit allowing solenoid valve 16a to close.

If ram 8b extends more than ram 8a, the tension on cable 50b will decrease and this will be detected by sensor 18b (FIG. 10). This decrease will cause the switch 27b to close and thus energize solenoid valve 16b (FIG. 7) opening the said valve and allowing fluid to escape from cylinder 7b. This will cause ram 8b to descend until the cable tension increases enough to allow sensor 18b to return to neutral, as in FIG. 8. This will break the circuit allowing valve 16b to close.

The system shown in FIG. 13 will cause the rams 8a and 8b to maintain the same amount of extension as long as electrical energy is supplied. Since it provides an independent means for the escape of fluid from beneath the rams 8a and 8b it will operate whether the rams are ascending, descending or stationary.

The application of the lift and leveling circuits to the lifting and transporting of containers or other loads is accomplished by a rectangular frame 10 suspended within the main frame of the vehicle by cables 11, 11a, 11b, 11c, FIGS. 2, 3 and 5. The lifting beam 10 may have any of several methods for attaching it to a load. It is shown here equipped with a twist lock type of mechanism 83 (FIG. 3) which has become a standard in the containerized freight industry. Such twist lock mechanism is disclosed in US. Pat. No. 2,963,310 issued Dec. 9, 1960. It is engaged by being inserted into a suitable socket which is integral with the load, and is then rotated about 90 degrees within the socket. It will thus support the attached load until it is disengaged by the operator. In this machine the force required to lock and unlock is supplied by an hydraulic cylinder on the frame 10 (not shown). The operator controls the application of this force by a control valve 85 (FIG. 6)

located in the operators cab 79. The hydraulic pump 84 (FIG. 6) to operate this circuit is located on the engine and may serve as a source of power for several other functions.

Near the end of the lifting beam 10 (FIG. 5) adjacent the arch 72 is located a guide bar 86 disposed across lifting beam 10 and projecting beyond it at both sides. The guide bar 86 is carried in a slotted opening in the lifting beam 10 so that it may move either fore and aft or laterally with relation to the lifting beam 10. The guide bar 86 has a roller 88 (FIG. 2) attached to each end. These rollers 88 move vertically in tracks 89, which are mounted on the arch diagonal legs 73 and 73a, by use of track guides 90 (FIGS. 1,2, 5 and 5a) disposed thereon near the top of diagonal legs 73 and 73a. The tracks 89 can be moved vertically in these guides 90. They rest in sockets fitting 91 (FIG. 1) on main frames 70 and 71. As long as the guide bar 86 operates below the tops of the arch 72 (FIGS. 1 and 3) no movement of tracks 89 occurs. When the guide bar 86 is elevated above this point, as in FIGS. 2 and 4 however caps 106 (FIGS. 1, 2 and 4) at the tops of the tracks 89 are engaged by the guide bar 86 and the tracks '89 are elevated with it. As the beam 10 with guide bar 86 is lowered, the tracks 89 descend with it until their lower ends rest in socket fittings 91 on the main lower frame members 70 and 71. From this point downward travel is guided by rollers 88 descending in the tracks 89.

The guide bar 86 has a lateral extension 87 in the form of an A-frame attached to it which extends to the opposite end of the lifting beam 10, as shown in FIG. 5. The guide bar 86 and A-frame 87 are caused to maintain the same lateral and fore and aft position in relation to the main frame of the machine by the actions of the tracks 89. They thus serve as a base for the lateral control of the lifting beam 10.

The guide bar 86 and A-frame 87 and the lifting beam 10 are connected near each end by double-acting hydraulic cylinders 92 and 93, as shown in FIG. 5 and FIG. 6. Cylinders 92 and 93 are arranged so as to impart relative movement to lifting beam 10 in a lateral direction (crosswise of the machine), and a cylinder 94 is arranged to impart relative movement to lifting beam 10 in a fore-and-aft direction. The cylinders 92, 93 and 94 have independent separate controls 95 and 96 and 97 (FIG. 6) in the operator's cab 79. Thus it is possible for the operator to move either end of the lifting beam 10 in a lateral direction, or to move the lifting beam 10 fore-and-aft with relation to the guide bar 86 and A- frame 87, and hence to the rest of the vehicle. He can also cause any combination of the two movements to occur.

The beam shift controls (FIG. 6) are in the form of an hydraulic control valve which has a hold or no flow position when the valve is in neutral. Thus the shift cylinders will hold the beam 10 in whatever position the operator desires. Each valve 95 and 96 is connected to its respective cylinder by two hydraulic conduits. The braking and acceleration loads imposed on lifting beam 10 are transferred to the guide bar 86 through cylinder 94 and A-frame 87.

Because the hydrostatic drive employed in this machine allows precision control in a fore-and-aft direction, it is likely that some operators will not feel 

1. A straddle carrier consisting of a pair of spaced parallel elongated frame members adapted to straddle a load; a single vertically disposed arch member connecting said frame members together adjacent one end thereof; diagonally disposed leg members connecting the top of the arch member to said frame members intermediate the ends thereof forming an open ended vertically unobstructed bay between said frame members rearwardly of said arch member; ground wheels flexibly and steerably mounted on the undersides of the frame members; means for driving certain of said wheels; a rectangular load lifting beam disposed between the frame members; extensible upright support means spaced along each frame member, and flexible lifting means guided over the upper end of each support means and engaging the four corners of the lifting beam for raising and lowering the lifting beam; means at the four corners of the lifting beam for securing the same to a load; means adjacent the arch member for guiding the lifting beam during its ascent and descent; and means controlling the lifting beam raising and lowering means whereby the four corners of said beam will be simultaneously raised or lowered equal amounts notwithstanding the relative weights on said respective corners in order to maintain the beam always parallel with the said frame members.
 1. A straddle carrier consisting of a pair of spaced parallel elongated frame members adapted to straddle a load; a single vertically disposed arch member connecting said frame members together adjacent one end thereof; diagonally disposed leg members connecting the top of the arch member to said frame members intermediate the ends thereof forming an open ended vertically unobstructed bay between said frame members rearwardly of said arch member; ground wheels flexibly and steerably mounted on the undersides of the frame members; means for driving certain of said wheels; a rectangular load lifting beam disposed between the frame members; extensible upright support means spaced along each frame member, and flexible lifting means guided over the upper end of each support means and engaging the four corners of the lifting beam for raising and lowering the lifting beam; means at the four corners of the lifting beam for securing the same to a load; means adjacent the arch member for guiding the lifting beam during its ascent and descent; and means controlling the lifting beam raising and lowering means whereby the four corners of said beam will be simultaneously raised or lowered equal amounts notwithstanding the relative weights on said respective corners in order to maintain the beam always parallel with the said frame members.
 2. In a carrier as set forth in claim 1, said driving means comprising drive motors mounted in the hubs of one end wheel of each frame member; an engine driven variable displacement pump mounted on one frame member, flexible piping connecting the pump with said motors respectively; a cab mounted on the outer face of the top of said arch member; and means in said cab for controlling said pump.
 3. In a carrier as set forth in claim 1, said load lifting beam comprising a rectangular frame; a transverse guide bar extending through slotted openings in the lifting beam so as to be shiftable fore-and-aft and laterally with respect to the lifting beams; rollers carried by the ends of the guide bar; said guide bar being disposed near the end of the lifting beam adjacent to the arch member; an A-frame extending from the guide bar within the lifting frame and having its apex terminating adjacent the opposite end of the lifting beam; a double-acting hydraulic cylinder connecting the said opposite end of the lifting beam to the apex of the A-frame and adapted to impart relative movement of the A-frame and lifting beam in a fore-and-aft direction; other double-acting hydraulic cylinders connecting the guide bar and the adjacent end of the lifting beam adapted to impart relative movement of thE A-frame and lifting beam in a lateral direction; a cab mounted on the outer face of the top of said arch member; and means in said cab for controlling said cylinders.
 4. In a carrier as set forth in claim 3, a lifting beam control comprising an hydraulic circuit including a tank, a pump, said first and other double-acting hydraulic cylinders, and normally closed hydraulic valves adapted when open to allow fluid to flow from one end of their respective double-acting hydraulic cylinders to the other end, and when closed to hold the lifting beam in adjusted position.
 5. In a carrier as set forth in claim 4, said normally closed hydraulic valves having controls, an electric circuit including the controls of the normally closed hydraulic valves, and a single switch which when closed will cause the said controls to be energized simultaneously, thereby allowing the lifting beam to ''''float'''', and when open will allow the said controls to be operated individually.
 6. In a carrier as set forth in claim 1, said load lifting beam comprising a rectangular frame; a transverse guide bar extending through slotted openings in the lifting beam so as to be shiftable laterally with respect to the lifting beams; rollers carried by the ends of the guide bar; said guide bar being disposed near the end of the lifting beam adjacent to the arch member; an A-frame extending from the guide bar within the lifting frame and having its apex terminating adjacent the opposite end of the lifting beam; double-acting hydraulic cylinders connecting the lifting beam to the apex of the A-frame and to the transverse guide respectively adapted to impart relative movement of the A-frame and transverse guide in a lateral direction; a cab mounted on the outer face of the top of said arch member; and means in said cab for controlling said cylinders.
 7. In a carrier as set forth in claim 1, said means for guiding said lifting beam comprising telescoping tracks on the arch diagonal leg members receiving rollers on the lifting beam, said tracks being movable vertically in guides disposed adjacent the tops of the leg members, said tracks being of such height that as long as the lifting beam is operating below the top of the arch member no movement of the tracks will occur, but when the lifting beam is elevated above the arch member the rollers will engage caps at the tops of the tracks and will elevate the tracks in their guides with the lifting beam; and sockets on the carrier frame members below the tracks normally receiving the lower ends of the tracks.
 8. In a carrier as set forth in claim 1, said lifting beam raising and lowering means comprising independent free double-acting hydraulic cylinders having their lower ends connected by self-aligning bearings to the frame members adjacent the corners of the lifting beam; said cylinders adjacent the arch member being loosely confined in and extending freely through openings therefor in the upper ends of the diagonal brace members; channel-shaped columns extending upwardly from the frame members at the end opposite from the arch member, said channels loosely confining the said cylinders at the end of the frame members opposite from the arch member, and having straps across their upper ends for preventing the related cylinders from falling inwardly under no-load conditions; upwardly movable rams in said cylinders respectively; pulleys mounted on the upper ends of the rams respectively; cables connected with the four corners of the lifting beam respectively and extending over said pulleys with their outer ends adjustably secured to anchors on the brace members and said columns respectively, whereby as the rams are simultaneously activated the corners of the lifting beam will be simultaneously correspondingly vertically moved; said cylinders and rams normally leaning inwardly at their upper ends, and being free to equalize the forces acting on the lifting beam and anchors through said cables without subjection to any bending loads.
 9. In A carrier as set forth in claim 1, said controlling means comprising a fluid circuit including a fluid tank, a pump, an operator-controlled valve, and a flow divider; said divider dividing the fluid delivered thereto into four substantially equal parts each of which parts is delivered to a related check valve at the lowe end of its related flexibly mounted hydraulic cylinder to move its related ram; said check valves having pilot pistons therein adapted to open when fluid is passing thereto, said fluid escaping through said check valves and passing back to the tank, and said pistons closing when no fluid pressure is exerted thereon, thereby stopping movement of the related ram; said check valves discharging into the upper and lower ends of the hydraulic cylinders, electric control means for maintaining equal ram extension when ascending, descending or when stationary; whereby the operator may control the speed of ascent and descent of the lifting beam by controlling the speed of the pump.
 10. In combination with a carrier as set forth in claim 9, means for sensing uneven extensions of the rams due to variations in load on the four corners of the lifting beam, comprising cables each having one end connected to a ram respectively, said cable being threaded through a sheave at the base of the related cylinder through a sensor, through a second sheave at the base of an adjacent cylinder, over a third sheave at the top of the ram of the adjacent cylinder, and under a fourth sheave attached to the adjacent corner of the lifting beam, its other end being attached to the ram of the adjacent cylinder, whereby as the lifting beam is elevated the cable will be paid out between the fourth and third sheaves twice as fast as the increase in distance between the third and second sheaves, the tension on the cable remaining constant as long as the rams extend equal amounts, but if one ram should extend more than the other, the variation in tension on the cable will be detected by the sensor and the related valve will open allowing fluid to escape from the related cylinder, allowing the related ram to move until the cable tension changes thereby permitting the sensor to return to neutral position.
 11. In a carrier as set forth in claim 10, said sensor comprising a base, a swingable lever pivoted at one end on the base, a pair of spaced pulleys journaled on the lever; said cable passing under one pulley, between and over the other pulley; microswitches on the base disposed at opposite sides of the lever one of which is adapted to be actuated as the lever is swung from central neutral position by variation in tension in the cable to a position over said one microswitch; spring means normally urging the lever to overcome the cable tension; said valves being solenoid controlled valves; and an electric circuit including a battery, said valves, and said microswitches.
 12. In a wheeled vehicle, a load lifting beam comprising a rectangular frame; a transverse guide bar extending through slotted openings in the lifting beam so as to be shiftable fore-and-aft and laterally with respect to the lifting beams; rollers carried by the ends of the guide bar; said guide bar being disposed near one end of the lifting beam; an A-frame extending from the guide bar within the lifting frame and having its apex terminating adjacent the opposite end of the lifting beam; means for guiding said lifting beam; means for raising and lowering the lifting beam; a double-acting hydraulic cylinder connecting the said opposite end of the lifting beam to the apex of the A-frame and adapted to impart relative movement of the A-frame and lifting beam in a fore-and-aft direction; other double-acting hydraulic cylinders connecting the guide bar and the adjacent end of the lifting beam adapted to impart relative movement of the A-frame and lifting beam in a lateral direction; and means for controlling said cylinders.
 13. In a vehicle as set forth in claim 12, said means for guiding said lifting beam comprising tElescoping tracks on vehicle receiving said rollers, said tracks being movable vertically in guides and being of such height that as long as the lifting beam is operating below the tops of the tracks no moment of the tracks will occur, but when the lifting beam is elevated above the tops of the tracks the rollers will engage caps at the tops of the tracks and will elevate the tracks in their guides with the lifting beam; and sockets on the carrier vehicle below the tracks normally receiving the lower ends of the tracks.
 14. In a vehicle as set forth in claim 12, said lifting beam raising and lowering means comprising independent upwardly disposed free double-acting hydraulic cylinders having their lower ends connected by self-aligning bearings to the vehicle adjacent the corners of the lifting beam; said cylinders at one end of the vehicle being loosely confined in and extending freely through openings therefor in the upper end of the vehicle frame; channel-shaped columns extending upwardly from the vehicle at the opposite end of the lifting beam, said channels loosely confining the said cylinders at the said end of the vehicle, and having straps across their upper ends for preventing the related cylinders from falling inwardly under no-load conditions; upwardly movable rams in said cylinders respectively; pulleys mounted on the upper ends of the rams respectively, cables connected with the four corners of the lifting beam respectively and extending over said pulleys with their outer ends adjustably secured to anchors on the frame and the said columns respectively, whereby as the rams are simultaneously activated the corners of the lifting beam will be simultaneously correspondingly vertically moved; said cylinders and rams normally leaning inwardly at their upper ends, and being free to equalize the forces acting on the lifting beam and anchors through said cables without being subjected to any bending loads.
 15. In a vehicle as set forth in claim 12, said controlling means comprising a fluid circuit including a fluid tank, a pump, an operator-controlled valve, and a flow divider, said divider dividing the fluid delivered thereto into four substantially equal parts, each of which parts is delivered to a related check valve at the lower end of its related hydraulic cylinder to move its related ram; said check valves having pilot pistons therein adapted to open when fluid is passing thereto, said fluid escaping through said check valves and passing back to the tank, and said pistons closing when no fluid pressure is exerted thereon, thereby stopping movement of the related ram; said check valves discharging into the upper and lower ends of the hydraulic cylinders whereby the operator may control the speed of ascent and descent of the lifting beam by controlling the speed of the pump.
 16. In combination with a vehicle as set forth in claim 15, means for sensing uneven extensions of the rams due to variations in load on the four corners of the lifting beam, comprising cables each having one end connected to a ram respectively, said cable being threaded through a sheave at the base of the related cylinder through a sensor, through a second sheave at the base of an adjacent cylinder, over a third sheave at the top of the ram of the adjacent cylinder, and under a fourth sheave attached to the adjacent corner of the lifting beam, its other end being attached to the ram of the adjacent cylinder, whereby as the lifting beam is elevated the cable will be paid out between the fourth and third sheaves twice as fast as the increase in distance between the third and second sheaves, whereby the tension on the cable will remain constant as long as the rams extend an equal amount, but if one ram should extend more than the other, the changed tension on the cable will be detected by the sensor and the related valve will open allowing fluid to escape from the related cylinder, allowing the related ram to move until the cable tension changes, thereby permitting the sensor to return to Neutral position. 